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Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC vs.
Revision 1.268 by root, Tue May 30 22:45:52 2017 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my ($fh) = @_;	10	my $fh = shift
		11	or die "/etc/passwd: $!";
11	...	12	...
12	};	13	};
13		14
14	aio_unlink "/tmp/file", sub { };	15	aio_unlink "/tmp/file", sub { };
15		16
…		…
25	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
26		27
27	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
28	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
29		30
30	# AnyEvent integration
31	open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
32	my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
33
34	# Event integration
35	Event->io (fd => IO::AIO::poll_fileno,
36	poll => 'r',
37	cb => \&IO::AIO::poll_cb);
38
39	# Glib/Gtk2 integration
40	add_watch Glib::IO IO::AIO::poll_fileno,
41	in => sub { IO::AIO::poll_cb; 1 };
42
43	# Tk integration
44	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
45	readable => \&IO::AIO::poll_cb);
46
47	# Danga::Socket integration
48	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
49	\&IO::AIO::poll_cb);
50
51	=head1 DESCRIPTION	31	=head1 DESCRIPTION
52		32
53	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
54	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
55		36
56	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
57	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
58	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
59	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
61	etc.), but can also be used to easily do operations in parallel that are	42	etc.), but can also be used to easily do operations in parallel that are
62	normally done sequentially, e.g. stat'ing many files, which is much faster	43	normally done sequentially, e.g. stat'ing many files, which is much faster
63	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
64	concurrently.	45	concurrently.
65		46
66	While this works on all types of file descriptors (for example sockets),	47	While most of this works on all types of file descriptors (for
67	using these functions on file descriptors that support nonblocking	48	example sockets), using these functions on file descriptors that
68	operation (again, sockets, pipes etc.) is very inefficient. Use an event	49	support nonblocking operation (again, sockets, pipes etc.) is
69	loop for that (such as the L<Event|Event> module): IO::AIO will naturally	50	very inefficient. Use an event loop for that (such as the L<EV>
70	fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
71		52
72	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
73	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
74	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
75	to perl. In the future, this module might make use of the native aio	56	to perl. In the future, this module might make use of the native aio
…		…
77	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
78	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
79	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
80	using threads anyway.	61	using threads anyway.
81		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
82	Although the module will work with in the presence of other (Perl-)	67	Although the module will work in the presence of other (Perl-) threads,
83	threads, it is currently not reentrant in any way, so use appropriate	68	it is currently not reentrant in any way, so use appropriate locking
84	locking yourself, always call C<poll_cb> from within the same thread, or	69	yourself, always call C<poll_cb> from within the same thread, or never
85	never call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
		71
		72	=head2 EXAMPLE
		73
		74	This is a simple example that uses the EV module and loads
		75	F</etc/passwd> asynchronously:
		76
		77	use EV;
		78	use IO::AIO;
		79
		80	# register the IO::AIO callback with EV
		81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		82
		83	# queue the request to open /etc/passwd
		84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
		85	my $fh = shift
		86	or die "error while opening: $!";
		87
		88	# stat'ing filehandles is generally non-blocking
		89	my $size = -s $fh;
		90
		91	# queue a request to read the file
		92	my $contents;
		93	aio_read $fh, 0, $size, $contents, 0, sub {
		94	$_[0] == $size
		95	or die "short read: $!";
		96
		97	close $fh;
		98
		99	# file contents now in $contents
		100	print $contents;
		101
		102	# exit event loop and program
		103	EV::break;
		104	};
		105	};
		106
		107	# possibly queue up other requests, or open GUI windows,
		108	# check for sockets etc. etc.
		109
		110	# process events as long as there are some:
		111	EV::run;
86		112
87	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
88		114
89	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
90	directly visible to Perl.	116	directly visible to Perl.
…		…
132	Request has reached the end of its lifetime and holds no resources anymore	158	Request has reached the end of its lifetime and holds no resources anymore
133	(except possibly for the Perl object, but its connection to the actual	159	(except possibly for the Perl object, but its connection to the actual
134	aio request is severed and calling its methods will either do nothing or	160	aio request is severed and calling its methods will either do nothing or
135	result in a runtime error).	161	result in a runtime error).
136		162
		163	=back
		164
137	=cut	165	=cut
138		166
139	package IO::AIO;	167	package IO::AIO;
140		168
141	no warnings;	169	use Carp ();
142	use strict 'vars';	170
		171	use common::sense;
143		172
144	use base 'Exporter';	173	use base 'Exporter';
145		174
146	BEGIN {	175	BEGIN {
147	our $VERSION = '2.0';	176	our $VERSION = 4.35;
148		177
149	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
150	aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
151	aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
152	aio_copy aio_group aio_nop aio_mknod);	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
		183	aio_rename aio_link aio_move aio_copy aio_group
		184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
		185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
		189
153	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
154	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
155	min_parallel max_parallel nreqs nready npending);	192	min_parallel max_parallel max_idle idle_timeout
		193	nreqs nready npending nthreads
		194	max_poll_time max_poll_reqs
		195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
		197
		198	push @AIO_REQ, qw(aio_busy); # not exported
156		199
157	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
158		201
159	require XSLoader;	202	require XSLoader;
160	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
161	}	204	}
162		205
163	=head1 FUNCTIONS	206	=head1 FUNCTIONS
164		207
165	=head2 AIO FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_mkdir $pathname, $mode, $callback->($status)
		239	aio_rmdir $pathname, $callback->($status)
		240	aio_readdir $pathname, $callback->($entries)
		241	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		242	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		243	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		244	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		245	aio_load $pathname, $data, $callback->($status)
		246	aio_copy $srcpath, $dstpath, $callback->($status)
		247	aio_move $srcpath, $dstpath, $callback->($status)
		248	aio_rmtree $pathname, $callback->($status)
		249	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		250	aio_ioctl $fh, $request, $buf, $callback->($status)
		251	aio_sync $callback->($status)
		252	aio_syncfs $fh, $callback->($status)
		253	aio_fsync $fh, $callback->($status)
		254	aio_fdatasync $fh, $callback->($status)
		255	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		256	aio_pathsync $pathname, $callback->($status)
		257	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		258	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		259	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		260	aio_mlockall $flags, $callback->($status)
		261	aio_group $callback->(...)
		262	aio_nop $callback->()
		263
		264	$prev_pri = aioreq_pri [$pri]
		265	aioreq_nice $pri_adjust
		266
		267	IO::AIO::poll_wait
		268	IO::AIO::poll_cb
		269	IO::AIO::poll
		270	IO::AIO::flush
		271	IO::AIO::max_poll_reqs $nreqs
		272	IO::AIO::max_poll_time $seconds
		273	IO::AIO::min_parallel $nthreads
		274	IO::AIO::max_parallel $nthreads
		275	IO::AIO::max_idle $nthreads
		276	IO::AIO::idle_timeout $seconds
		277	IO::AIO::max_outstanding $maxreqs
		278	IO::AIO::nreqs
		279	IO::AIO::nready
		280	IO::AIO::npending
		281
		282	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		283	IO::AIO::fadvise $fh, $offset, $len, $advice
		284	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		285	IO::AIO::munmap $scalar
		286	IO::AIO::madvise $scalar, $offset, $length, $advice
		287	IO::AIO::mprotect $scalar, $offset, $length, $protect
		288	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		289	IO::AIO::munlockall
		290
		291	=head2 API NOTES
166		292
167	All the C<aio_*> calls are more or less thin wrappers around the syscall	293	All the C<aio_*> calls are more or less thin wrappers around the syscall
168	with the same name (sans C<aio_>). The arguments are similar or identical,	294	with the same name (sans C<aio_>). The arguments are similar or identical,
169	and they all accept an additional (and optional) C<$callback> argument	295	and they all accept an additional (and optional) C<$callback> argument
170	which must be a code reference. This code reference will get called with	296	which must be a code reference. This code reference will be called after
171	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	297	the syscall has been executed in an asynchronous fashion. The results
172	perl, which usually delivers "false") as it's sole argument when the given	298	of the request will be passed as arguments to the callback (and, if an
173	syscall has been executed asynchronously.	299	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		300	most syscalls return C<-1> on error, unlike perl, which usually delivers
		301	"false").
		302
		303	Some requests (such as C<aio_readdir>) pass the actual results and
		304	communicate failures by passing C<undef>.
174		305
175	All functions expecting a filehandle keep a copy of the filehandle	306	All functions expecting a filehandle keep a copy of the filehandle
176	internally until the request has finished.	307	internally until the request has finished.
177		308
178	All requests return objects of type L<IO::AIO::REQ> that allow further	309	All functions return request objects of type L<IO::AIO::REQ> that allow
179	manipulation of those requests while they are in-flight.	310	further manipulation of those requests while they are in-flight.
180		311
181	The pathnames you pass to these routines I<must> be absolute and	312	The pathnames you pass to these routines I<should> be absolute. The
182	encoded in byte form. The reason for the former is that at the time the	313	reason for this is that at the time the request is being executed, the
183	request is being executed, the current working directory could have	314	current working directory could have changed. Alternatively, you can
184	changed. Alternatively, you can make sure that you never change the	315	make sure that you never change the current working directory anywhere
185	current working directory.	316	in the program and then use relative paths. You can also take advantage
		317	of IO::AIOs working directory abstraction, that lets you specify paths
		318	relative to some previously-opened "working directory object" - see the
		319	description of the C<IO::AIO::WD> class later in this document.
186		320
187	To encode pathnames to byte form, either make sure you either: a)	321	To encode pathnames as octets, either make sure you either: a) always pass
188	always pass in filenames you got from outside (command line, readdir	322	in filenames you got from outside (command line, readdir etc.) without
189	etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode	323	tinkering, b) are in your native filesystem encoding, c) use the Encode
190	your pathnames to the locale (or other) encoding in effect in the user	324	module and encode your pathnames to the locale (or other) encoding in
191	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	325	effect in the user environment, d) use Glib::filename_from_unicode on
192	use something else.	326	unicode filenames or e) use something else to ensure your scalar has the
		327	correct contents.
		328
		329	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
		330	handles correctly whether it is set or not.
		331
		332	=head2 AIO REQUEST FUNCTIONS
193		333
194	=over 4	334	=over 4
195		335
196	=item $prev_pri = aioreq_pri [$pri]	336	=item $prev_pri = aioreq_pri [$pri]
197		337
…		…
217	aio_read $_[0], ..., sub {	357	aio_read $_[0], ..., sub {
218	...	358	...
219	};	359	};
220	};	360	};
221		361
		362
222	=item aioreq_nice $pri_adjust	363	=item aioreq_nice $pri_adjust
223		364
224	Similar to C<aioreq_pri>, but subtracts the given value from the current	365	Similar to C<aioreq_pri>, but subtracts the given value from the current
225	priority, so effects are cumulative.	366	priority, so the effect is cumulative.
		367
226		368
227	=item aio_open $pathname, $flags, $mode, $callback->($fh)	369	=item aio_open $pathname, $flags, $mode, $callback->($fh)
228		370
229	Asynchronously open or create a file and call the callback with a newly	371	Asynchronously open or create a file and call the callback with a newly
230	created filehandle for the file.	372	created filehandle for the file (or C<undef> in case of an error).
231		373
232	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	374	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
233	for an explanation.	375	for an explanation.
234		376
235	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	377	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
236	list. They are the same as used by C<sysopen>.	378	list. They are the same as used by C<sysopen>.
237		379
238	Likewise, C<$mode> specifies the mode of the newly created file, if it	380	Likewise, C<$mode> specifies the mode of the newly created file, if it
239	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,	381	didn't exist and C<O_CREAT> has been given, just like perl's C<sysopen>,
240	except that it is mandatory (i.e. use C<0> if you don't create new files,	382	except that it is mandatory (i.e. use C<0> if you don't create new files,
241	and C<0666> or C<0777> if you do).	383	and C<0666> or C<0777> if you do). Note that the C<$mode> will be modified
		384	by the umask in effect then the request is being executed, so better never
		385	change the umask.
242		386
243	Example:	387	Example:
244		388
245	aio_open "/etc/passwd", O_RDONLY, 0, sub {	389	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
246	if ($_[0]) {	390	if ($_[0]) {
247	print "open successful, fh is $_[0]\n";	391	print "open successful, fh is $_[0]\n";
248	...	392	...
249	} else {	393	} else {
250	die "open failed: $!\n";	394	die "open failed: $!\n";
251	}	395	}
252	};	396	};
253		397
		398	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		399	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		400	following POSIX and non-POSIX constants are available (missing ones on
		401	your system are, as usual, C<0>):
		402
		403	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		404	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		405	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		406
		407
254	=item aio_close $fh, $callback->($status)	408	=item aio_close $fh, $callback->($status)
255		409
256	Asynchronously close a file and call the callback with the result	410	Asynchronously close a file and call the callback with the result
257	code. I<WARNING:> although accepted, you should not pass in a perl	411	code.
258	filehandle here, as perl will likely close the file descriptor another
259	time when the filehandle is destroyed. Normally, you can safely call perls
260	C<close> or just let filehandles go out of scope.
261		412
262	This is supposed to be a bug in the API, so that might change. It's	413	Unfortunately, you can't do this to perl. Perl I<insists> very strongly on
263	therefore best to avoid this function.	414	closing the file descriptor associated with the filehandle itself.
		415
		416	Therefore, C<aio_close> will not close the filehandle - instead it will
		417	use dup2 to overwrite the file descriptor with the write-end of a pipe
		418	(the pipe fd will be created on demand and will be cached).
		419
		420	Or in other words: the file descriptor will be closed, but it will not be
		421	free for reuse until the perl filehandle is closed.
		422
		423	=cut
		424
		425	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		426
		427	Seeks the filehandle to the new C<$offset>, similarly to perl's
		428	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		429	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		430	C<IO::AIO::SEEK_END>).
		431
		432	The resulting absolute offset will be passed to the callback, or C<-1> in
		433	case of an error.
		434
		435	In theory, the C<$whence> constants could be different than the
		436	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		437	so don't panic.
		438
		439	As a GNU/Linux (and maybe Solaris) extension, also the constants
		440	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		441	could be found. No guarantees about suitability for use in C<aio_seek> or
		442	Perl's C<sysseek> can be made though, although I would naively assume they
		443	"just work".
264		444
265	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	445	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
266		446
267	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	447	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
268		448
269	Reads or writes C<length> bytes from the specified C<fh> and C<offset>	449	Reads or writes C<$length> bytes from or to the specified C<$fh> and
270	into the scalar given by C<data> and offset C<dataoffset> and calls the	450	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
271	callback without the actual number of bytes read (or -1 on error, just	451	calls the callback with the actual number of bytes transferred (or -1 on
272	like the syscall).	452	error, just like the syscall).
		453
		454	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
		455	offset plus the actual number of bytes read.
		456
		457	If C<$offset> is undefined, then the current file descriptor offset will
		458	be used (and updated), otherwise the file descriptor offset will not be
		459	changed by these calls.
		460
		461	If C<$length> is undefined in C<aio_write>, use the remaining length of
		462	C<$data>.
		463
		464	If C<$dataoffset> is less than zero, it will be counted from the end of
		465	C<$data>.
273		466
274	The C<$data> scalar I<MUST NOT> be modified in any way while the request	467	The C<$data> scalar I<MUST NOT> be modified in any way while the request
275	is outstanding. Modifying it can result in segfaults or WW3 (if the	468	is outstanding. Modifying it can result in segfaults or World War III (if
276	necessary/optional hardware is installed).	469	the necessary/optional hardware is installed).
277		470
278	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at	471	Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
279	offset C<0> within the scalar:	472	offset C<0> within the scalar:
280		473
281	aio_read $fh, 7, 15, $buffer, 0, sub {	474	aio_read $fh, 7, 15, $buffer, 0, sub {
282	$_[0] > 0 or die "read error: $!";	475	$_[0] > 0 or die "read error: $!";
283	print "read $_[0] bytes: <$buffer>\n";	476	print "read $_[0] bytes: <$buffer>\n";
284	};	477	};
285		478
		479
286	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)	480	=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
287		481
288	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	482	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
289	reading at byte offset C<$in_offset>, and starts writing at the current	483	reading at byte offset C<$in_offset>, and starts writing at the current
290	file offset of C<$out_fh>. Because of that, it is not safe to issue more	484	file offset of C<$out_fh>. Because of that, it is not safe to issue more
291	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	485	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
292	other.	486	other. The same C<$in_fh> works fine though, as this function does not
		487	move or use the file offset of C<$in_fh>.
293		488
		489	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		490	are written, and there is no way to find out how many more bytes have been
		491	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		492	number of bytes written to C<$out_fh>. Only if the result value equals
		493	C<$length> one can assume that C<$length> bytes have been read.
		494
		495	Unlike with other C<aio_> functions, it makes a lot of sense to use
		496	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		497	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		498	the socket I/O will be non-blocking. Note, however, that you can run
		499	into a trap where C<aio_sendfile> reads some data with readahead, then
		500	fails to write all data, and when the socket is ready the next time, the
		501	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		502	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		503	resource usage.
		504
294	This call tries to make use of a native C<sendfile> syscall to provide	505	This call tries to make use of a native C<sendfile>-like syscall to
295	zero-copy operation. For this to work, C<$out_fh> should refer to a	506	provide zero-copy operation. For this to work, C<$out_fh> should refer to
296	socket, and C<$in_fh> should refer to mmap'able file.	507	a socket, and C<$in_fh> should refer to an mmap'able file.
297		508
298	If the native sendfile call fails or is not implemented, it will be	509	If a native sendfile cannot be found or it fails with C<ENOSYS>,
299	emulated, so you can call C<aio_sendfile> on any type of filehandle	510	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		511	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
300	regardless of the limitations of the operating system.	512	type of filehandle regardless of the limitations of the operating system.
301		513
302	Please note, however, that C<aio_sendfile> can read more bytes from	514	As native sendfile syscalls (as practically any non-POSIX interface hacked
303	C<$in_fh> than are written, and there is no way to find out how many	515	together in a hurry to improve benchmark numbers) tend to be rather buggy
304	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	516	on many systems, this implementation tries to work around some known bugs
305	provides the number of bytes written to C<$out_fh>. Only if the result	517	in Linux and FreeBSD kernels (probably others, too), but that might fail,
306	value equals C<$length> one can assume that C<$length> bytes have been	518	so you really really should check the return value of C<aio_sendfile> -
307	read.	519	fewer bytes than expected might have been transferred.
		520
308		521
309	=item aio_readahead $fh,$offset,$length, $callback->($retval)	522	=item aio_readahead $fh,$offset,$length, $callback->($retval)
310		523
311	C<aio_readahead> populates the page cache with data from a file so that	524	C<aio_readahead> populates the page cache with data from a file so that
312	subsequent reads from that file will not block on disk I/O. The C<$offset>	525	subsequent reads from that file will not block on disk I/O. The C<$offset>
…		…
315	whole pages, so that offset is effectively rounded down to a page boundary	528	whole pages, so that offset is effectively rounded down to a page boundary
316	and bytes are read up to the next page boundary greater than or equal to	529	and bytes are read up to the next page boundary greater than or equal to
317	(off-set+length). C<aio_readahead> does not read beyond the end of the	530	(off-set+length). C<aio_readahead> does not read beyond the end of the
318	file. The current file offset of the file is left unchanged.	531	file. The current file offset of the file is left unchanged.
319		532
320	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	533	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
321	emulated by simply reading the data, which would have a similar effect.	534	be emulated by simply reading the data, which would have a similar effect.
		535
322		536
323	=item aio_stat $fh_or_path, $callback->($status)	537	=item aio_stat $fh_or_path, $callback->($status)
324		538
325	=item aio_lstat $fh, $callback->($status)	539	=item aio_lstat $fh, $callback->($status)
326		540
…		…
332	for an explanation.	546	for an explanation.
333		547
334	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	548	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
335	error when stat'ing a large file, the results will be silently truncated	549	error when stat'ing a large file, the results will be silently truncated
336	unless perl itself is compiled with large file support.	550	unless perl itself is compiled with large file support.
		551
		552	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		553	following constants and functions (if not implemented, the constants will
		554	be C<0> and the functions will either C<croak> or fall back on traditional
		555	behaviour).
		556
		557	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		558	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		559	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
337		560
338	Example: Print the length of F</etc/passwd>:	561	Example: Print the length of F</etc/passwd>:
339		562
340	aio_stat "/etc/passwd", sub {	563	aio_stat "/etc/passwd", sub {
341	$_[0] and die "stat failed: $!";	564	$_[0] and die "stat failed: $!";
342	print "size is ", -s _, "\n";	565	print "size is ", -s _, "\n";
343	};	566	};
344		567
		568
		569	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		570
		571	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		572	whether a file handle or path was passed.
		573
		574	On success, the callback is passed a hash reference with the following
		575	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		576	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		577	is passed.
		578
		579	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		580	C<ST_NOSUID>.
		581
		582	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		583	their correct value when available, or to C<0> on systems that do
		584	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		585	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		586	C<ST_NODIRATIME> and C<ST_RELATIME>.
		587
		588	Example: stat C</wd> and dump out the data if successful.
		589
		590	aio_statvfs "/wd", sub {
		591	my $f = $_[0]
		592	or die "statvfs: $!";
		593
		594	use Data::Dumper;
		595	say Dumper $f;
		596	};
		597
		598	# result:
		599	{
		600	bsize => 1024,
		601	bfree => 4333064312,
		602	blocks => 10253828096,
		603	files => 2050765568,
		604	flag => 4096,
		605	favail => 2042092649,
		606	bavail => 4333064312,
		607	ffree => 2042092649,
		608	namemax => 255,
		609	frsize => 1024,
		610	fsid => 1810
		611	}
		612
		613	Here is a (likely partial - send me updates!) list of fsid values used by
		614	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		615
		616	0x0000adf5 adfs
		617	0x0000adff affs
		618	0x5346414f afs
		619	0x09041934 anon-inode filesystem
		620	0x00000187 autofs
		621	0x42465331 befs
		622	0x1badface bfs
		623	0x42494e4d binfmt_misc
		624	0x9123683e btrfs
		625	0x0027e0eb cgroupfs
		626	0xff534d42 cifs
		627	0x73757245 coda
		628	0x012ff7b7 coh
		629	0x28cd3d45 cramfs
		630	0x453dcd28 cramfs-wend (wrong endianness)
		631	0x64626720 debugfs
		632	0x00001373 devfs
		633	0x00001cd1 devpts
		634	0x0000f15f ecryptfs
		635	0x00414a53 efs
		636	0x0000137d ext
		637	0x0000ef53 ext2/ext3/ext4
		638	0x0000ef51 ext2
		639	0xf2f52010 f2fs
		640	0x00004006 fat
		641	0x65735546 fuseblk
		642	0x65735543 fusectl
		643	0x0bad1dea futexfs
		644	0x01161970 gfs2
		645	0x47504653 gpfs
		646	0x00004244 hfs
		647	0xf995e849 hpfs
		648	0x00c0ffee hostfs
		649	0x958458f6 hugetlbfs
		650	0x2bad1dea inotifyfs
		651	0x00009660 isofs
		652	0x000072b6 jffs2
		653	0x3153464a jfs
		654	0x6b414653 k-afs
		655	0x0bd00bd0 lustre
		656	0x0000137f minix
		657	0x0000138f minix 30 char names
		658	0x00002468 minix v2
		659	0x00002478 minix v2 30 char names
		660	0x00004d5a minix v3
		661	0x19800202 mqueue
		662	0x00004d44 msdos
		663	0x0000564c novell
		664	0x00006969 nfs
		665	0x6e667364 nfsd
		666	0x00003434 nilfs
		667	0x5346544e ntfs
		668	0x00009fa1 openprom
		669	0x7461636F ocfs2
		670	0x00009fa0 proc
		671	0x6165676c pstorefs
		672	0x0000002f qnx4
		673	0x68191122 qnx6
		674	0x858458f6 ramfs
		675	0x52654973 reiserfs
		676	0x00007275 romfs
		677	0x67596969 rpc_pipefs
		678	0x73636673 securityfs
		679	0xf97cff8c selinux
		680	0x0000517b smb
		681	0x534f434b sockfs
		682	0x73717368 squashfs
		683	0x62656572 sysfs
		684	0x012ff7b6 sysv2
		685	0x012ff7b5 sysv4
		686	0x01021994 tmpfs
		687	0x15013346 udf
		688	0x00011954 ufs
		689	0x54190100 ufs byteswapped
		690	0x00009fa2 usbdevfs
		691	0x01021997 v9fs
		692	0xa501fcf5 vxfs
		693	0xabba1974 xenfs
		694	0x012ff7b4 xenix
		695	0x58465342 xfs
		696	0x012fd16d xia
		697
		698	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		699
		700	Works like perl's C<utime> function (including the special case of $atime
		701	and $mtime being undef). Fractional times are supported if the underlying
		702	syscalls support them.
		703
		704	When called with a pathname, uses utimes(2) if available, otherwise
		705	utime(2). If called on a file descriptor, uses futimes(2) if available,
		706	otherwise returns ENOSYS, so this is not portable.
		707
		708	Examples:
		709
		710	# set atime and mtime to current time (basically touch(1)):
		711	aio_utime "path", undef, undef;
		712	# set atime to current time and mtime to beginning of the epoch:
		713	aio_utime "path", time, undef; # undef==0
		714
		715
		716	=item aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		717
		718	Works like perl's C<chown> function, except that C<undef> for either $uid
		719	or $gid is being interpreted as "do not change" (but -1 can also be used).
		720
		721	Examples:
		722
		723	# same as "chown root path" in the shell:
		724	aio_chown "path", 0, -1;
		725	# same as above:
		726	aio_chown "path", 0, undef;
		727
		728
		729	=item aio_truncate $fh_or_path, $offset, $callback->($status)
		730
		731	Works like truncate(2) or ftruncate(2).
		732
		733
		734	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		735
		736	Allocates or frees disk space according to the C<$mode> argument. See the
		737	linux C<fallocate> documentation for details.
		738
		739	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		740	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		741	to deallocate a file range.
		742
		743	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		744	(without leaving a hole) and C<FALLOC_FL_ZERO_RANGE>, to zero a range (see
		745	your L<fallocate(2)> manpage).
		746
		747	The file system block size used by C<fallocate> is presumably the
		748	C<f_bsize> returned by C<statvfs>.
		749
		750	If C<fallocate> isn't available or cannot be emulated (currently no
		751	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		752
		753
		754	=item aio_chmod $fh_or_path, $mode, $callback->($status)
		755
		756	Works like perl's C<chmod> function.
		757
		758
345	=item aio_unlink $pathname, $callback->($status)	759	=item aio_unlink $pathname, $callback->($status)
346		760
347	Asynchronously unlink (delete) a file and call the callback with the	761	Asynchronously unlink (delete) a file and call the callback with the
348	result code.	762	result code.
349		763
		764
350	=item aio_mknod $path, $mode, $dev, $callback->($status)	765	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
		766
		767	[EXPERIMENTAL]
351		768
352	Asynchronously create a device node (or fifo). See mknod(2).	769	Asynchronously create a device node (or fifo). See mknod(2).
353		770
354	The only portable (POSIX) way of calling this function is:	771	The only (POSIX-) portable way of calling this function is:
355		772
356	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	773	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
		774
		775	See C<aio_stat> for info about some potentially helpful extra constants
		776	and functions.
357		777
358	=item aio_link $srcpath, $dstpath, $callback->($status)	778	=item aio_link $srcpath, $dstpath, $callback->($status)
359		779
360	Asynchronously create a new link to the existing object at C<$srcpath> at	780	Asynchronously create a new link to the existing object at C<$srcpath> at
361	the path C<$dstpath> and call the callback with the result code.	781	the path C<$dstpath> and call the callback with the result code.
362		782
		783
363	=item aio_symlink $srcpath, $dstpath, $callback->($status)	784	=item aio_symlink $srcpath, $dstpath, $callback->($status)
364		785
365	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	786	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
366	the path C<$dstpath> and call the callback with the result code.	787	the path C<$dstpath> and call the callback with the result code.
367		788
		789
		790	=item aio_readlink $pathname, $callback->($link)
		791
		792	Asynchronously read the symlink specified by C<$path> and pass it to
		793	the callback. If an error occurs, nothing or undef gets passed to the
		794	callback.
		795
		796
		797	=item aio_realpath $pathname, $callback->($path)
		798
		799	Asynchronously make the path absolute and resolve any symlinks in
		800	C<$path>. The resulting path only consists of directories (same as
		801	L<Cwd::realpath>).
		802
		803	This request can be used to get the absolute path of the current working
		804	directory by passing it a path of F<.> (a single dot).
		805
		806
368	=item aio_rename $srcpath, $dstpath, $callback->($status)	807	=item aio_rename $srcpath, $dstpath, $callback->($status)
369		808
370	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	809	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
371	rename(2) and call the callback with the result code.	810	rename(2) and call the callback with the result code.
372		811
		812	On systems that support the AIO::WD working directory abstraction
		813	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		814	of failing, C<rename> is called on the absolute path of C<$wd>.
		815
		816
		817	=item aio_mkdir $pathname, $mode, $callback->($status)
		818
		819	Asynchronously mkdir (create) a directory and call the callback with
		820	the result code. C<$mode> will be modified by the umask at the time the
		821	request is executed, so do not change your umask.
		822
		823
373	=item aio_rmdir $pathname, $callback->($status)	824	=item aio_rmdir $pathname, $callback->($status)
374		825
375	Asynchronously rmdir (delete) a directory and call the callback with the	826	Asynchronously rmdir (delete) a directory and call the callback with the
376	result code.	827	result code.
		828
		829	On systems that support the AIO::WD working directory abstraction
		830	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		831	C<rmdir> is called on the absolute path of C<$wd>.
		832
377		833
378	=item aio_readdir $pathname, $callback->($entries)	834	=item aio_readdir $pathname, $callback->($entries)
379		835
380	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	836	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
381	directory (i.e. opendir + readdir + closedir). The entries will not be	837	directory (i.e. opendir + readdir + closedir). The entries will not be
382	sorted, and will B<NOT> include the C<.> and C<..> entries.	838	sorted, and will B<NOT> include the C<.> and C<..> entries.
383		839
384	The callback a single argument which is either C<undef> or an array-ref	840	The callback is passed a single argument which is either C<undef> or an
385	with the filenames.	841	array-ref with the filenames.
		842
		843
		844	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		845
		846	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
		847	tune behaviour and output format. In case of an error, C<$entries> will be
		848	C<undef>.
		849
		850	The flags are a combination of the following constants, ORed together (the
		851	flags will also be passed to the callback, possibly modified):
		852
		853	=over 4
		854
		855	=item IO::AIO::READDIR_DENTS
		856
		857	When this flag is off, then the callback gets an arrayref consisting of
		858	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
		859	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
		860	entry in more detail.
		861
		862	C<$name> is the name of the entry.
		863
		864	C<$type> is one of the C<IO::AIO::DT_xxx> constants:
		865
		866	C<IO::AIO::DT_UNKNOWN>, C<IO::AIO::DT_FIFO>, C<IO::AIO::DT_CHR>, C<IO::AIO::DT_DIR>,
		867	C<IO::AIO::DT_BLK>, C<IO::AIO::DT_REG>, C<IO::AIO::DT_LNK>, C<IO::AIO::DT_SOCK>,
		868	C<IO::AIO::DT_WHT>.
		869
		870	C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
		871	know, you have to run stat yourself. Also, for speed reasons, the C<$type>
		872	scalars are read-only: you can not modify them.
		873
		874	C<$inode> is the inode number (which might not be exact on systems with 64
		875	bit inode numbers and 32 bit perls). This field has unspecified content on
		876	systems that do not deliver the inode information.
		877
		878	=item IO::AIO::READDIR_DIRS_FIRST
		879
		880	When this flag is set, then the names will be returned in an order where
		881	likely directories come first, in optimal stat order. This is useful when
		882	you need to quickly find directories, or you want to find all directories
		883	while avoiding to stat() each entry.
		884
		885	If the system returns type information in readdir, then this is used
		886	to find directories directly. Otherwise, likely directories are names
		887	beginning with ".", or otherwise names with no dots, of which names with
		888	short names are tried first.
		889
		890	=item IO::AIO::READDIR_STAT_ORDER
		891
		892	When this flag is set, then the names will be returned in an order
		893	suitable for stat()'ing each one. That is, when you plan to stat()
		894	all files in the given directory, then the returned order will likely
		895	be fastest.
		896
		897	If both this flag and C<IO::AIO::READDIR_DIRS_FIRST> are specified, then
		898	the likely dirs come first, resulting in a less optimal stat order.
		899
		900	=item IO::AIO::READDIR_FOUND_UNKNOWN
		901
		902	This flag should not be set when calling C<aio_readdirx>. Instead, it
		903	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
		904	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
		905	C<$type>'s are known, which can be used to speed up some algorithms.
		906
		907	=back
		908
		909
		910	=item aio_load $pathname, $data, $callback->($status)
		911
		912	This is a composite request that tries to fully load the given file into
		913	memory. Status is the same as with aio_read.
		914
		915	=cut
		916
		917	sub aio_load($$;$) {
		918	my ($path, undef, $cb) = @_;
		919	my $data = \$_[1];
		920
		921	my $pri = aioreq_pri;
		922	my $grp = aio_group $cb;
		923
		924	aioreq_pri $pri;
		925	add $grp aio_open $path, O_RDONLY, 0, sub {
		926	my $fh = shift
		927	or return $grp->result (-1);
		928
		929	aioreq_pri $pri;
		930	add $grp aio_read $fh, 0, (-s $fh), $$data, 0, sub {
		931	$grp->result ($_[0]);
		932	};
		933	};
		934
		935	$grp
		936	}
386		937
387	=item aio_copy $srcpath, $dstpath, $callback->($status)	938	=item aio_copy $srcpath, $dstpath, $callback->($status)
388		939
389	Try to copy the I<file> (directories not supported as either source or	940	Try to copy the I<file> (directories not supported as either source or
390	destination) from C<$srcpath> to C<$dstpath> and call the callback with	941	destination) from C<$srcpath> to C<$dstpath> and call the callback with
391	the C<0> (error) or C<-1> ok.	942	a status of C<0> (ok) or C<-1> (error, see C<$!>).
392		943
393	This is a composite request that it creates the destination file with	944	This is a composite request that creates the destination file with
394	mode 0200 and copies the contents of the source file into it using	945	mode 0200 and copies the contents of the source file into it using
395	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	946	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
396	uid/gid, in that order.	947	uid/gid, in that order.
397		948
398	If an error occurs, the partial destination file will be unlinked, if	949	If an error occurs, the partial destination file will be unlinked, if
…		…
408	my $grp = aio_group $cb;	959	my $grp = aio_group $cb;
409		960
410	aioreq_pri $pri;	961	aioreq_pri $pri;
411	add $grp aio_open $src, O_RDONLY, 0, sub {	962	add $grp aio_open $src, O_RDONLY, 0, sub {
412	if (my $src_fh = $_[0]) {	963	if (my $src_fh = $_[0]) {
413	my @stat = stat $src_fh;	964	my @stat = stat $src_fh; # hmm, might block over nfs?
414		965
415	aioreq_pri $pri;	966	aioreq_pri $pri;
416	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	967	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
417	if (my $dst_fh = $_[0]) {	968	if (my $dst_fh = $_[0]) {
418	aioreq_pri $pri;	969	aioreq_pri $pri;
419	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {	970	add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
420	if ($_[0] == $stat[7]) {	971	if ($_[0] == $stat[7]) {
421	$grp->result (0);	972	$grp->result (0);
422	close $src_fh;	973	close $src_fh;
423		974
424	# those should not normally block. should. should.	975	my $ch = sub {
		976	aioreq_pri $pri;
		977	add $grp aio_chmod $dst_fh, $stat[2] & 07777, sub {
		978	aioreq_pri $pri;
		979	add $grp aio_chown $dst_fh, $stat[4], $stat[5], sub {
		980	aioreq_pri $pri;
		981	add $grp aio_close $dst_fh;
		982	}
		983	};
		984	};
		985
		986	aioreq_pri $pri;
		987	add $grp aio_utime $dst_fh, $stat[8], $stat[9], sub {
		988	if ($_[0] < 0 && $! == ENOSYS) {
		989	aioreq_pri $pri;
425	utime $stat[8], $stat[9], $dst;	990	add $grp aio_utime $dst, $stat[8], $stat[9], $ch;
426	chmod $stat[2] & 07777, $dst_fh;	991	} else {
427	chown $stat[4], $stat[5], $dst_fh;	992	$ch->();
		993	}
428	close $dst_fh;	994	};
429	} else {	995	} else {
430	$grp->result (-1);	996	$grp->result (-1);
431	close $src_fh;	997	close $src_fh;
432	close $dst_fh;	998	close $dst_fh;
433		999
…		…
450		1016
451	=item aio_move $srcpath, $dstpath, $callback->($status)	1017	=item aio_move $srcpath, $dstpath, $callback->($status)
452		1018
453	Try to move the I<file> (directories not supported as either source or	1019	Try to move the I<file> (directories not supported as either source or
454	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1020	destination) from C<$srcpath> to C<$dstpath> and call the callback with
455	the C<0> (error) or C<-1> ok.	1021	a status of C<0> (ok) or C<-1> (error, see C<$!>).
456		1022
457	This is a composite request that tries to rename(2) the file first. If	1023	This is a composite request that tries to rename(2) the file first; if
458	rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if	1024	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
459	that is successful, unlinking the C<$srcpath>.	1025	that is successful, unlinks the C<$srcpath>.
460		1026
461	=cut	1027	=cut
462		1028
463	sub aio_move($$;$) {	1029	sub aio_move($$;$) {
464	my ($src, $dst, $cb) = @_;	1030	my ($src, $dst, $cb) = @_;
…		…
471	if ($_[0] && $! == EXDEV) {	1037	if ($_[0] && $! == EXDEV) {
472	aioreq_pri $pri;	1038	aioreq_pri $pri;
473	add $grp aio_copy $src, $dst, sub {	1039	add $grp aio_copy $src, $dst, sub {
474	$grp->result ($_[0]);	1040	$grp->result ($_[0]);
475		1041
476	if (!$_[0]) {	1042	unless ($_[0]) {
477	aioreq_pri $pri;	1043	aioreq_pri $pri;
478	add $grp aio_unlink $src;	1044	add $grp aio_unlink $src;
479	}	1045	}
480	};	1046	};
481	} else {	1047	} else {
…		…
484	};	1050	};
485		1051
486	$grp	1052	$grp
487	}	1053	}
488		1054
489	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1055	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
490		1056
491	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1057	Scans a directory (similar to C<aio_readdir>) but additionally tries to
492	efficiently separate the entries of directory C<$path> into two sets of	1058	efficiently separate the entries of directory C<$path> into two sets of
493	names, directories you can recurse into (directories), and ones you cannot	1059	names, directories you can recurse into (directories), and ones you cannot
494	recurse into (everything else, including symlinks to directories).	1060	recurse into (everything else, including symlinks to directories).
…		…
511		1077
512	Implementation notes.	1078	Implementation notes.
513		1079
514	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.	1080	The C<aio_readdir> cannot be avoided, but C<stat()>'ing every entry can.
515		1081
		1082	If readdir returns file type information, then this is used directly to
		1083	find directories.
		1084
516	After reading the directory, the modification time, size etc. of the	1085	Otherwise, after reading the directory, the modification time, size etc.
517	directory before and after the readdir is checked, and if they match (and	1086	of the directory before and after the readdir is checked, and if they
518	isn't the current time), the link count will be used to decide how many	1087	match (and isn't the current time), the link count will be used to decide
519	entries are directories (if >= 2). Otherwise, no knowledge of the number	1088	how many entries are directories (if >= 2). Otherwise, no knowledge of the
520	of subdirectories will be assumed.	1089	number of subdirectories will be assumed.
521		1090
522	Then entries will be sorted into likely directories (everything without	1091	Then entries will be sorted into likely directories a non-initial dot
523	a non-initial dot currently) and likely non-directories (everything	1092	currently) and likely non-directories (see C<aio_readdirx>). Then every
524	else). Then every entry plus an appended C</.> will be C<stat>'ed,	1093	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
525	likely directories first. If that succeeds, it assumes that the entry	1094	in order of their inode numbers. If that succeeds, it assumes that the
526	is a directory or a symlink to directory (which will be checked	1095	entry is a directory or a symlink to directory (which will be checked
527	seperately). This is often faster than stat'ing the entry itself because	1096	separately). This is often faster than stat'ing the entry itself because
528	filesystems might detect the type of the entry without reading the inode	1097	filesystems might detect the type of the entry without reading the inode
529	data (e.g. ext2fs filetype feature).	1098	data (e.g. ext2fs filetype feature), even on systems that cannot return
		1099	the filetype information on readdir.
530		1100
531	If the known number of directories (link count - 2) has been reached, the	1101	If the known number of directories (link count - 2) has been reached, the
532	rest of the entries is assumed to be non-directories.	1102	rest of the entries is assumed to be non-directories.
533		1103
534	This only works with certainty on POSIX (= UNIX) filesystems, which	1104	This only works with certainty on POSIX (= UNIX) filesystems, which
…		…
538	as those tend to return 0 or 1 as link counts, which disables the	1108	as those tend to return 0 or 1 as link counts, which disables the
539	directory counting heuristic.	1109	directory counting heuristic.
540		1110
541	=cut	1111	=cut
542		1112
543	sub aio_scandir($$$) {	1113	sub aio_scandir($$;$) {
544	my ($path, $maxreq, $cb) = @_;	1114	my ($path, $maxreq, $cb) = @_;
545		1115
546	my $pri = aioreq_pri;	1116	my $pri = aioreq_pri;
547		1117
548	my $grp = aio_group $cb;	1118	my $grp = aio_group $cb;
549		1119
550	$maxreq = 4 if $maxreq <= 0;	1120	$maxreq = 4 if $maxreq <= 0;
551		1121
552	# stat once	1122	# get a wd object
553	aioreq_pri $pri;	1123	aioreq_pri $pri;
554	add $grp aio_stat $path, sub {	1124	add $grp aio_wd $path, sub {
		1125	$_[0]
555	return $grp->result () if $_[0];	1126	or return $grp->result ();
556	my $now = time;
557	my $hash1 = join ":", (stat _)[0,1,3,7,9];
558		1127
559	# read the directory entries	1128	my $wd = [shift, "."];
		1129
		1130	# stat once
560	aioreq_pri $pri;	1131	aioreq_pri $pri;
561	add $grp aio_readdir $path, sub {	1132	add $grp aio_stat $wd, sub {
562	my $entries = shift
563	or return $grp->result ();	1133	return $grp->result () if $_[0];
		1134	my $now = time;
		1135	my $hash1 = join ":", (stat _)[0,1,3,7,9];
564		1136
565	# stat the dir another time	1137	# read the directory entries
566	aioreq_pri $pri;	1138	aioreq_pri $pri;
		1139	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1140	my $entries = shift
		1141	or return $grp->result ();
		1142
		1143	# stat the dir another time
		1144	aioreq_pri $pri;
567	add $grp aio_stat $path, sub {	1145	add $grp aio_stat $wd, sub {
568	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1146	my $hash2 = join ":", (stat _)[0,1,3,7,9];
569		1147
570	my $ndirs;	1148	my $ndirs;
571		1149
572	# take the slow route if anything looks fishy	1150	# take the slow route if anything looks fishy
573	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1151	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
574	$ndirs = -1;	1152	$ndirs = -1;
575	} else {	1153	} else {
576	# if nlink == 2, we are finished	1154	# if nlink == 2, we are finished
577	# on non-posix-fs's, we rely on nlink < 2	1155	# for non-posix-fs's, we rely on nlink < 2
578	$ndirs = (stat _)[3] - 2	1156	$ndirs = (stat _)[3] - 2
579	or return $grp->result ([], $entries);	1157	or return $grp->result ([], $entries);
580	}	1158	}
581		1159
582	# sort into likely dirs and likely nondirs
583	# dirs == files without ".", short entries first
584	$entries = [map $_->[0],
585	sort { $b->[1] cmp $a->[1] }
586	map [$_, sprintf "%s%04d", (/.\./ ? "1" : "0"), length],
587	@$entries];
588
589	my (@dirs, @nondirs);	1160	my (@dirs, @nondirs);
590		1161
591	my $statgrp = add $grp aio_group sub {	1162	my $statgrp = add $grp aio_group sub {
592	$grp->result (\@dirs, \@nondirs);	1163	$grp->result (\@dirs, \@nondirs);
593	};	1164	};
594		1165
595	limit $statgrp $maxreq;	1166	limit $statgrp $maxreq;
596	feed $statgrp sub {	1167	feed $statgrp sub {
597	return unless @$entries;	1168	return unless @$entries;
598	my $entry = pop @$entries;	1169	my $entry = shift @$entries;
599		1170
600	aioreq_pri $pri;	1171	aioreq_pri $pri;
		1172	$wd->[1] = "$entry/.";
601	add $statgrp aio_stat "$path/$entry/.", sub {	1173	add $statgrp aio_stat $wd, sub {
602	if ($_[0] < 0) {	1174	if ($_[0] < 0) {
603	push @nondirs, $entry;	1175	push @nondirs, $entry;
604	} else {	1176	} else {
605	# need to check for real directory	1177	# need to check for real directory
606	aioreq_pri $pri;	1178	aioreq_pri $pri;
		1179	$wd->[1] = $entry;
607	add $statgrp aio_lstat "$path/$entry", sub {	1180	add $statgrp aio_lstat $wd, sub {
608	if (-d _) {	1181	if (-d _) {
609	push @dirs, $entry;	1182	push @dirs, $entry;
610		1183
611	unless (--$ndirs) {	1184	unless (--$ndirs) {
612	push @nondirs, @$entries;	1185	push @nondirs, @$entries;
613	feed $statgrp;	1186	feed $statgrp;
		1187	}
		1188	} else {
		1189	push @nondirs, $entry;
614	}	1190	}
615	} else {
616	push @nondirs, $entry;
617	}	1191	}
618	}	1192	}
619	}	1193	};
620	};	1194	};
621	};	1195	};
622	};	1196	};
623	};	1197	};
624	};	1198	};
625		1199
626	$grp	1200	$grp
627	}	1201	}
628		1202
		1203	=item aio_rmtree $pathname, $callback->($status)
		1204
		1205	Delete a directory tree starting (and including) C<$path>, return the
		1206	status of the final C<rmdir> only. This is a composite request that
		1207	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
		1208	everything else.
		1209
		1210	=cut
		1211
		1212	sub aio_rmtree;
		1213	sub aio_rmtree($;$) {
		1214	my ($path, $cb) = @_;
		1215
		1216	my $pri = aioreq_pri;
		1217	my $grp = aio_group $cb;
		1218
		1219	aioreq_pri $pri;
		1220	add $grp aio_scandir $path, 0, sub {
		1221	my ($dirs, $nondirs) = @_;
		1222
		1223	my $dirgrp = aio_group sub {
		1224	add $grp aio_rmdir $path, sub {
		1225	$grp->result ($_[0]);
		1226	};
		1227	};
		1228
		1229	(aioreq_pri $pri), add $dirgrp aio_rmtree "$path/$_" for @$dirs;
		1230	(aioreq_pri $pri), add $dirgrp aio_unlink "$path/$_" for @$nondirs;
		1231
		1232	add $grp $dirgrp;
		1233	};
		1234
		1235	$grp
		1236	}
		1237
		1238	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1239
		1240	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1241
		1242	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1243	they execute asynchronously and pass the return value to the callback.
		1244
		1245	Both calls can be used for a lot of things, some of which make more sense
		1246	to run asynchronously in their own thread, while some others make less
		1247	sense. For example, calls that block waiting for external events, such
		1248	as locking, will also lock down an I/O thread while it is waiting, which
		1249	can deadlock the whole I/O system. At the same time, there might be no
		1250	alternative to using a thread to wait.
		1251
		1252	So in general, you should only use these calls for things that do
		1253	(filesystem) I/O, not for things that wait for other events (network,
		1254	other processes), although if you are careful and know what you are doing,
		1255	you still can.
		1256
		1257	The following constants are available (missing ones are, as usual C<0>):
		1258
		1259	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1260
		1261	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1262	C<FS_IOC_FIEMAP>.
		1263
		1264	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1265	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1266
		1267	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1268	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1269	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1270	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1271	C<FS_FL_USER_MODIFIABLE>.
		1272
		1273	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1274	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1275	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1276	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1277
		1278	=item aio_sync $callback->($status)
		1279
		1280	Asynchronously call sync and call the callback when finished.
		1281
629	=item aio_fsync $fh, $callback->($status)	1282	=item aio_fsync $fh, $callback->($status)
630		1283
631	Asynchronously call fsync on the given filehandle and call the callback	1284	Asynchronously call fsync on the given filehandle and call the callback
632	with the fsync result code.	1285	with the fsync result code.
633		1286
…		…
636	Asynchronously call fdatasync on the given filehandle and call the	1289	Asynchronously call fdatasync on the given filehandle and call the
637	callback with the fdatasync result code.	1290	callback with the fdatasync result code.
638		1291
639	If this call isn't available because your OS lacks it or it couldn't be	1292	If this call isn't available because your OS lacks it or it couldn't be
640	detected, it will be emulated by calling C<fsync> instead.	1293	detected, it will be emulated by calling C<fsync> instead.
		1294
		1295	=item aio_syncfs $fh, $callback->($status)
		1296
		1297	Asynchronously call the syncfs syscall to sync the filesystem associated
		1298	to the given filehandle and call the callback with the syncfs result
		1299	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1300	errno to C<ENOSYS> nevertheless.
		1301
		1302	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		1303
		1304	Sync the data portion of the file specified by C<$offset> and C<$length>
		1305	to disk (but NOT the metadata), by calling the Linux-specific
		1306	sync_file_range call. If sync_file_range is not available or it returns
		1307	ENOSYS, then fdatasync or fsync is being substituted.
		1308
		1309	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
		1310	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
		1311	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
		1312	manpage for details.
		1313
		1314	=item aio_pathsync $pathname, $callback->($status)
		1315
		1316	This request tries to open, fsync and close the given path. This is a
		1317	composite request intended to sync directories after directory operations
		1318	(E.g. rename). This might not work on all operating systems or have any
		1319	specific effect, but usually it makes sure that directory changes get
		1320	written to disc. It works for anything that can be opened for read-only,
		1321	not just directories.
		1322
		1323	Future versions of this function might fall back to other methods when
		1324	C<fsync> on the directory fails (such as calling C<sync>).
		1325
		1326	Passes C<0> when everything went ok, and C<-1> on error.
		1327
		1328	=cut
		1329
		1330	sub aio_pathsync($;$) {
		1331	my ($path, $cb) = @_;
		1332
		1333	my $pri = aioreq_pri;
		1334	my $grp = aio_group $cb;
		1335
		1336	aioreq_pri $pri;
		1337	add $grp aio_open $path, O_RDONLY, 0, sub {
		1338	my ($fh) = @_;
		1339	if ($fh) {
		1340	aioreq_pri $pri;
		1341	add $grp aio_fsync $fh, sub {
		1342	$grp->result ($_[0]);
		1343
		1344	aioreq_pri $pri;
		1345	add $grp aio_close $fh;
		1346	};
		1347	} else {
		1348	$grp->result (-1);
		1349	}
		1350	};
		1351
		1352	$grp
		1353	}
		1354
		1355	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1356
		1357	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1358	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1359	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1360	scalar must only be modified in-place while an aio operation is pending on
		1361	it).
		1362
		1363	It calls the C<msync> function of your OS, if available, with the memory
		1364	area starting at C<$offset> in the string and ending C<$length> bytes
		1365	later. If C<$length> is negative, counts from the end, and if C<$length>
		1366	is C<undef>, then it goes till the end of the string. The flags can be
		1367	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1368	C<IO::AIO::MS_INVALIDATE>.
		1369
		1370	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1371
		1372	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1373	scalars.
		1374
		1375	It touches (reads or writes) all memory pages in the specified
		1376	range inside the scalar. All caveats and parameters are the same
		1377	as for C<aio_msync>, above, except for flags, which must be either
		1378	C<0> (which reads all pages and ensures they are instantiated) or
		1379	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1380	writing an octet from it, which dirties the page).
		1381
		1382	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1383
		1384	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1385	scalars.
		1386
		1387	It reads in all the pages of the underlying storage into memory (if any)
		1388	and locks them, so they are not getting swapped/paged out or removed.
		1389
		1390	If C<$length> is undefined, then the scalar will be locked till the end.
		1391
		1392	On systems that do not implement C<mlock>, this function returns C<-1>
		1393	and sets errno to C<ENOSYS>.
		1394
		1395	Note that the corresponding C<munlock> is synchronous and is
		1396	documented under L<MISCELLANEOUS FUNCTIONS>.
		1397
		1398	Example: open a file, mmap and mlock it - both will be undone when
		1399	C<$data> gets destroyed.
		1400
		1401	open my $fh, "<", $path or die "$path: $!";
		1402	my $data;
		1403	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1404	aio_mlock $data; # mlock in background
		1405
		1406	=item aio_mlockall $flags, $callback->($status)
		1407
		1408	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1409	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1410
		1411	On systems that do not implement C<mlockall>, this function returns C<-1>
		1412	and sets errno to C<ENOSYS>.
		1413
		1414	Note that the corresponding C<munlockall> is synchronous and is
		1415	documented under L<MISCELLANEOUS FUNCTIONS>.
		1416
		1417	Example: asynchronously lock all current and future pages into memory.
		1418
		1419	aio_mlockall IO::AIO::MCL_FUTURE;
		1420
		1421	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1422
		1423	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1424	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1425	the ioctl is not available on your OS, then this request will fail with
		1426	C<ENOSYS>.
		1427
		1428	C<$start> is the starting offset to query extents for, C<$length> is the
		1429	size of the range to query - if it is C<undef>, then the whole file will
		1430	be queried.
		1431
		1432	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1433	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1434	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1435	the data portion.
		1436
		1437	C<$count> is the maximum number of extent records to return. If it is
		1438	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1439	case, if it is C<0>, then the callback receives the number of extents
		1440	instead of the extents themselves (which is unreliable, see below).
		1441
		1442	If an error occurs, the callback receives no arguments. The special
		1443	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1444
		1445	Otherwise, the callback receives an array reference with extent
		1446	structures. Each extent structure is an array reference itself, with the
		1447	following members:
		1448
		1449	[$logical, $physical, $length, $flags]
		1450
		1451	Flags is any combination of the following flag values (typically either C<0>
		1452	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1453
		1454	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1455	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1456	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1457	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1458	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1459	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1460
		1461	At the time of this writing (Linux 3.2), this requets is unreliable unless
		1462	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1463	it to return all extents of a range for files with large number of
		1464	extents. The code works around all these issues if C<$count> is undef.
641		1465
642	=item aio_group $callback->(...)	1466	=item aio_group $callback->(...)
643		1467
644	This is a very special aio request: Instead of doing something, it is a	1468	This is a very special aio request: Instead of doing something, it is a
645	container for other aio requests, which is useful if you want to bundle	1469	container for other aio requests, which is useful if you want to bundle
…		…
683	immense (it blocks a thread for a long time) so do not use this function	1507	immense (it blocks a thread for a long time) so do not use this function
684	except to put your application under artificial I/O pressure.	1508	except to put your application under artificial I/O pressure.
685		1509
686	=back	1510	=back
687		1511
		1512
		1513	=head2 IO::AIO::WD - multiple working directories
		1514
		1515	Your process only has one current working directory, which is used by all
		1516	threads. This makes it hard to use relative paths (some other component
		1517	could call C<chdir> at any time, and it is hard to control when the path
		1518	will be used by IO::AIO).
		1519
		1520	One solution for this is to always use absolute paths. This usually works,
		1521	but can be quite slow (the kernel has to walk the whole path on every
		1522	access), and can also be a hassle to implement.
		1523
		1524	Newer POSIX systems have a number of functions (openat, fdopendir,
		1525	futimensat and so on) that make it possible to specify working directories
		1526	per operation.
		1527
		1528	For portability, and because the clowns who "designed", or shall I write,
		1529	perpetrated this new interface were obviously half-drunk, this abstraction
		1530	cannot be perfect, though.
		1531
		1532	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1533	object. This object stores the canonicalised, absolute version of the
		1534	path, and on systems that allow it, also a directory file descriptor.
		1535
		1536	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1537	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1538	object and a pathname instead (or the IO::AIO::WD object alone, which
		1539	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1540	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1541	to that IO::AIO::WD object.
		1542
		1543	For example, to get a wd object for F</etc> and then stat F<passwd>
		1544	inside, you would write:
		1545
		1546	aio_wd "/etc", sub {
		1547	my $etcdir = shift;
		1548
		1549	# although $etcdir can be undef on error, there is generally no reason
		1550	# to check for errors here, as aio_stat will fail with ENOENT
		1551	# when $etcdir is undef.
		1552
		1553	aio_stat [$etcdir, "passwd"], sub {
		1554	# yay
		1555	};
		1556	};
		1557
		1558	The fact that C<aio_wd> is a request and not a normal function shows that
		1559	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1560	which is why it is done asynchronously.
		1561
		1562	To stat the directory obtained with C<aio_wd> above, one could write
		1563	either of the following three request calls:
		1564
		1565	aio_lstat "/etc" , sub { ... # pathname as normal string
		1566	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1567	aio_lstat $wd , sub { ... # shorthand for the previous
		1568
		1569	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1570	object and the pathname string, so you could write the following without
		1571	causing any issues due to C<$path> getting reused:
		1572
		1573	my $path = [$wd, undef];
		1574
		1575	for my $name (qw(abc def ghi)) {
		1576	$path->[1] = $name;
		1577	aio_stat $path, sub {
		1578	# ...
		1579	};
		1580	}
		1581
		1582	There are some caveats: when directories get renamed (or deleted), the
		1583	pathname string doesn't change, so will point to the new directory (or
		1584	nowhere at all), while the directory fd, if available on the system,
		1585	will still point to the original directory. Most functions accepting a
		1586	pathname will use the directory fd on newer systems, and the string on
		1587	older systems. Some functions (such as realpath) will always rely on the
		1588	string form of the pathname.
		1589
		1590	So this functionality is mainly useful to get some protection against
		1591	C<chdir>, to easily get an absolute path out of a relative path for future
		1592	reference, and to speed up doing many operations in the same directory
		1593	(e.g. when stat'ing all files in a directory).
		1594
		1595	The following functions implement this working directory abstraction:
		1596
		1597	=over 4
		1598
		1599	=item aio_wd $pathname, $callback->($wd)
		1600
		1601	Asynchonously canonicalise the given pathname and convert it to an
		1602	IO::AIO::WD object representing it. If possible and supported on the
		1603	system, also open a directory fd to speed up pathname resolution relative
		1604	to this working directory.
		1605
		1606	If something goes wrong, then C<undef> is passwd to the callback instead
		1607	of a working directory object and C<$!> is set appropriately. Since
		1608	passing C<undef> as working directory component of a pathname fails the
		1609	request with C<ENOENT>, there is often no need for error checking in the
		1610	C<aio_wd> callback, as future requests using the value will fail in the
		1611	expected way.
		1612
		1613	=item IO::AIO::CWD
		1614
		1615	This is a compiletime constant (object) that represents the process
		1616	current working directory.
		1617
		1618	Specifying this object as working directory object for a pathname is as if
		1619	the pathname would be specified directly, without a directory object. For
		1620	example, these calls are functionally identical:
		1621
		1622	aio_stat "somefile", sub { ... };
		1623	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1624
		1625	=back
		1626
		1627	To recover the path associated with an IO::AIO::WD object, you can use
		1628	C<aio_realpath>:
		1629
		1630	aio_realpath $wd, sub {
		1631	warn "path is $_[0]\n";
		1632	};
		1633
		1634	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1635	sometimes, fall back to using an absolue path.
		1636
688	=head2 IO::AIO::REQ CLASS	1637	=head2 IO::AIO::REQ CLASS
689		1638
690	All non-aggregate C<aio_*> functions return an object of this class when	1639	All non-aggregate C<aio_*> functions return an object of this class when
691	called in non-void context.	1640	called in non-void context.
692		1641
…		…
695	=item cancel $req	1644	=item cancel $req
696		1645
697	Cancels the request, if possible. Has the effect of skipping execution	1646	Cancels the request, if possible. Has the effect of skipping execution
698	when entering the B<execute> state and skipping calling the callback when	1647	when entering the B<execute> state and skipping calling the callback when
699	entering the the B<result> state, but will leave the request otherwise	1648	entering the the B<result> state, but will leave the request otherwise
700	untouched. That means that requests that currently execute will not be	1649	untouched (with the exception of readdir). That means that requests that
701	stopped and resources held by the request will not be freed prematurely.	1650	currently execute will not be stopped and resources held by the request
		1651	will not be freed prematurely.
702		1652
703	=item cb $req $callback->(...)	1653	=item cb $req $callback->(...)
704		1654
705	Replace (or simply set) the callback registered to the request.	1655	Replace (or simply set) the callback registered to the request.
706		1656
…		…
757	Their lifetime, simplified, looks like this: when they are empty, they	1707	Their lifetime, simplified, looks like this: when they are empty, they
758	will finish very quickly. If they contain only requests that are in the	1708	will finish very quickly. If they contain only requests that are in the
759	C<done> state, they will also finish. Otherwise they will continue to	1709	C<done> state, they will also finish. Otherwise they will continue to
760	exist.	1710	exist.
761		1711
762	That means after creating a group you have some time to add requests. And	1712	That means after creating a group you have some time to add requests
763	in the callbacks of those requests, you can add further requests to the	1713	(precisely before the callback has been invoked, which is only done within
764	group. And only when all those requests have finished will the the group	1714	the C<poll_cb>). And in the callbacks of those requests, you can add
765	itself finish.	1715	further requests to the group. And only when all those requests have
		1716	finished will the the group itself finish.
766		1717
767	=over 4	1718	=over 4
768		1719
769	=item add $grp ...	1720	=item add $grp ...
770		1721
…		…
779	=item $grp->cancel_subs	1730	=item $grp->cancel_subs
780		1731
781	Cancel all subrequests and clears any feeder, but not the group request	1732	Cancel all subrequests and clears any feeder, but not the group request
782	itself. Useful when you queued a lot of events but got a result early.	1733	itself. Useful when you queued a lot of events but got a result early.
783		1734
		1735	The group request will finish normally (you cannot add requests to the
		1736	group).
		1737
784	=item $grp->result (...)	1738	=item $grp->result (...)
785		1739
786	Set the result value(s) that will be passed to the group callback when all	1740	Set the result value(s) that will be passed to the group callback when all
787	subrequests have finished and set thre groups errno to the current value	1741	subrequests have finished and set the groups errno to the current value
788	of errno (just like calling C<errno> without an error number). By default,	1742	of errno (just like calling C<errno> without an error number). By default,
789	no argument will be passed and errno is zero.	1743	no argument will be passed and errno is zero.
790		1744
791	=item $grp->errno ([$errno])	1745	=item $grp->errno ([$errno])
792		1746
…		…
803	=item feed $grp $callback->($grp)	1757	=item feed $grp $callback->($grp)
804		1758
805	Sets a feeder/generator on this group: every group can have an attached	1759	Sets a feeder/generator on this group: every group can have an attached
806	generator that generates requests if idle. The idea behind this is that,	1760	generator that generates requests if idle. The idea behind this is that,
807	although you could just queue as many requests as you want in a group,	1761	although you could just queue as many requests as you want in a group,
808	this might starve other requests for a potentially long time. For	1762	this might starve other requests for a potentially long time. For example,
809	example, C<aio_scandir> might generate hundreds of thousands C<aio_stat>	1763	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
810	requests, delaying any later requests for a long time.	1764	requests, delaying any later requests for a long time.
811		1765
812	To avoid this, and allow incremental generation of requests, you can	1766	To avoid this, and allow incremental generation of requests, you can
813	instead a group and set a feeder on it that generates those requests. The	1767	instead a group and set a feeder on it that generates those requests. The
814	feed callback will be called whenever there are few enough (see C<limit>,	1768	feed callback will be called whenever there are few enough (see C<limit>,
…		…
819	not impose any limits).	1773	not impose any limits).
820		1774
821	If the feed does not queue more requests when called, it will be	1775	If the feed does not queue more requests when called, it will be
822	automatically removed from the group.	1776	automatically removed from the group.
823		1777
824	If the feed limit is C<0>, it will be set to C<2> automatically.	1778	If the feed limit is C<0> when this method is called, it will be set to
		1779	C<2> automatically.
825		1780
826	Example:	1781	Example:
827		1782
828	# stat all files in @files, but only ever use four aio requests concurrently:	1783	# stat all files in @files, but only ever use four aio requests concurrently:
829		1784
…		…
841	Sets the feeder limit for the group: The feeder will be called whenever	1796	Sets the feeder limit for the group: The feeder will be called whenever
842	the group contains less than this many requests.	1797	the group contains less than this many requests.
843		1798
844	Setting the limit to C<0> will pause the feeding process.	1799	Setting the limit to C<0> will pause the feeding process.
845		1800
		1801	The default value for the limit is C<0>, but note that setting a feeder
		1802	automatically bumps it up to C<2>.
		1803
846	=back	1804	=back
847		1805
848	=head2 SUPPORT FUNCTIONS	1806	=head2 SUPPORT FUNCTIONS
849		1807
		1808	=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
		1809
850	=over 4	1810	=over 4
851		1811
852	=item $fileno = IO::AIO::poll_fileno	1812	=item $fileno = IO::AIO::poll_fileno
853		1813
854	Return the I<request result pipe file descriptor>. This filehandle must be	1814	Return the I<request result pipe file descriptor>. This filehandle must be
855	polled for reading by some mechanism outside this module (e.g. Event or	1815	polled for reading by some mechanism outside this module (e.g. EV, Glib,
856	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1816	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
857	to call C<poll_cb> to check the results.	1817	you have to call C<poll_cb> to check the results.
858		1818
859	See C<poll_cb> for an example.	1819	See C<poll_cb> for an example.
860		1820
861	=item IO::AIO::poll_cb	1821	=item IO::AIO::poll_cb
862		1822
863	Process all outstanding events on the result pipe. You have to call this	1823	Process some requests that have reached the result phase (i.e. they have
864	regularly. Returns the number of events processed. Returns immediately	1824	been executed but the results are not yet reported). You have to call
865	when no events are outstanding.	1825	this "regularly" to finish outstanding requests.
866		1826
		1827	Returns C<0> if all events could be processed (or there were no
		1828	events to process), or C<-1> if it returned earlier for whatever
		1829	reason. Returns immediately when no events are outstanding. The amount
		1830	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1831	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1832
867	If not all requests were processed for whatever reason, the filehandle	1833	If not all requests were processed for whatever reason, the poll file
868	will still be ready when C<poll_cb> returns.	1834	descriptor will still be ready when C<poll_cb> returns, so normally you
		1835	don't have to do anything special to have it called later.
		1836
		1837	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1838	ready, it can be beneficial to call this function from loops which submit
		1839	a lot of requests, to make sure the results get processed when they become
		1840	available and not just when the loop is finished and the event loop takes
		1841	over again. This function returns very fast when there are no outstanding
		1842	requests.
869		1843
870	Example: Install an Event watcher that automatically calls	1844	Example: Install an Event watcher that automatically calls
871	IO::AIO::poll_cb with high priority:	1845	IO::AIO::poll_cb with high priority (more examples can be found in the
		1846	SYNOPSIS section, at the top of this document):
872		1847
873	Event->io (fd => IO::AIO::poll_fileno,	1848	Event->io (fd => IO::AIO::poll_fileno,
874	poll => 'r', async => 1,	1849	poll => 'r', async => 1,
875	cb => \&IO::AIO::poll_cb);	1850	cb => \&IO::AIO::poll_cb);
876		1851
877	=item IO::AIO::poll_some $max_requests	1852	=item IO::AIO::poll_wait
878		1853
879	Similar to C<poll_cb>, but only processes up to C<$max_requests> requests	1854	Wait until either at least one request is in the result phase or no
880	at a time.	1855	requests are outstanding anymore.
881		1856
882	Useful if you want to ensure some level of interactiveness when perl is	1857	This is useful if you want to synchronously wait for some requests to
883	not fast enough to process all requests in time.	1858	become ready, without actually handling them.
		1859
		1860	See C<nreqs> for an example.
		1861
		1862	=item IO::AIO::poll
		1863
		1864	Waits until some requests have been handled.
		1865
		1866	Returns the number of requests processed, but is otherwise strictly
		1867	equivalent to:
		1868
		1869	IO::AIO::poll_wait, IO::AIO::poll_cb
		1870
		1871	=item IO::AIO::flush
		1872
		1873	Wait till all outstanding AIO requests have been handled.
		1874
		1875	Strictly equivalent to:
		1876
		1877	IO::AIO::poll_wait, IO::AIO::poll_cb
		1878	while IO::AIO::nreqs;
		1879
		1880	=item IO::AIO::max_poll_reqs $nreqs
		1881
		1882	=item IO::AIO::max_poll_time $seconds
		1883
		1884	These set the maximum number of requests (default C<0>, meaning infinity)
		1885	that are being processed by C<IO::AIO::poll_cb> in one call, respectively
		1886	the maximum amount of time (default C<0>, meaning infinity) spent in
		1887	C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
		1888	of time C<poll_cb> is allowed to use).
		1889
		1890	Setting C<max_poll_time> to a non-zero value creates an overhead of one
		1891	syscall per request processed, which is not normally a problem unless your
		1892	callbacks are really really fast or your OS is really really slow (I am
		1893	not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
		1894
		1895	Setting these is useful if you want to ensure some level of
		1896	interactiveness when perl is not fast enough to process all requests in
		1897	time.
		1898
		1899	For interactive programs, values such as C<0.01> to C<0.1> should be fine.
884		1900
885	Example: Install an Event watcher that automatically calls	1901	Example: Install an Event watcher that automatically calls
886	IO::AIO::poll_some with low priority, to ensure that other parts of the	1902	IO::AIO::poll_cb with low priority, to ensure that other parts of the
887	program get the CPU sometimes even under high AIO load.	1903	program get the CPU sometimes even under high AIO load.
888		1904
		1905	# try not to spend much more than 0.1s in poll_cb
		1906	IO::AIO::max_poll_time 0.1;
		1907
		1908	# use a low priority so other tasks have priority
889	Event->io (fd => IO::AIO::poll_fileno,	1909	Event->io (fd => IO::AIO::poll_fileno,
890	poll => 'r', nice => 1,	1910	poll => 'r', nice => 1,
891	cb => sub { IO::AIO::poll_some 256 });	1911	cb => &IO::AIO::poll_cb);
892		1912
893	=item IO::AIO::poll_wait	1913	=back
894		1914
895	Wait till the result filehandle becomes ready for reading (simply does a	1915	=head3 CONTROLLING THE NUMBER OF THREADS
896	C<select> on the filehandle. This is useful if you want to synchronously wait
897	for some requests to finish).
898		1916
899	See C<nreqs> for an example.	1917	=over
900
901	=item IO::AIO::nreqs
902
903	Returns the number of requests currently in the ready, execute or pending
904	states (i.e. for which their callback has not been invoked yet).
905
906	Example: wait till there are no outstanding requests anymore:
907
908	IO::AIO::poll_wait, IO::AIO::poll_cb
909	while IO::AIO::nreqs;
910
911	=item IO::AIO::nready
912
913	Returns the number of requests currently in the ready state (not yet
914	executed).
915
916	=item IO::AIO::npending
917
918	Returns the number of requests currently in the pending state (executed,
919	but not yet processed by poll_cb).
920
921	=item IO::AIO::flush
922
923	Wait till all outstanding AIO requests have been handled.
924
925	Strictly equivalent to:
926
927	IO::AIO::poll_wait, IO::AIO::poll_cb
928	while IO::AIO::nreqs;
929
930	=item IO::AIO::poll
931
932	Waits until some requests have been handled.
933
934	Strictly equivalent to:
935
936	IO::AIO::poll_wait, IO::AIO::poll_cb
937	if IO::AIO::nreqs;
938		1918
939	=item IO::AIO::min_parallel $nthreads	1919	=item IO::AIO::min_parallel $nthreads
940		1920
941	Set the minimum number of AIO threads to C<$nthreads>. The current	1921	Set the minimum number of AIO threads to C<$nthreads>. The current
942	default is C<8>, which means eight asynchronous operations can execute	1922	default is C<8>, which means eight asynchronous operations can execute
943	concurrently at any one time (the number of outstanding requests,	1923	concurrently at any one time (the number of outstanding requests,
944	however, is unlimited).	1924	however, is unlimited).
945		1925
946	IO::AIO starts threads only on demand, when an AIO request is queued and	1926	IO::AIO starts threads only on demand, when an AIO request is queued and
947	no free thread exists.	1927	no free thread exists. Please note that queueing up a hundred requests can
		1928	create demand for a hundred threads, even if it turns out that everything
		1929	is in the cache and could have been processed faster by a single thread.
948		1930
949	It is recommended to keep the number of threads relatively low, as some	1931	It is recommended to keep the number of threads relatively low, as some
950	Linux kernel versions will scale negatively with the number of threads	1932	Linux kernel versions will scale negatively with the number of threads
951	(higher parallelity => MUCH higher latency). With current Linux 2.6	1933	(higher parallelity => MUCH higher latency). With current Linux 2.6
952	versions, 4-32 threads should be fine.	1934	versions, 4-32 threads should be fine.
…		…
966	This module automatically runs C<max_parallel 0> at program end, to ensure	1948	This module automatically runs C<max_parallel 0> at program end, to ensure
967	that all threads are killed and that there are no outstanding requests.	1949	that all threads are killed and that there are no outstanding requests.
968		1950
969	Under normal circumstances you don't need to call this function.	1951	Under normal circumstances you don't need to call this function.
970		1952
		1953	=item IO::AIO::max_idle $nthreads
		1954
		1955	Limit the number of threads (default: 4) that are allowed to idle
		1956	(i.e., threads that did not get a request to process within the idle
		1957	timeout (default: 10 seconds). That means if a thread becomes idle while
		1958	C<$nthreads> other threads are also idle, it will free its resources and
		1959	exit.
		1960
		1961	This is useful when you allow a large number of threads (e.g. 100 or 1000)
		1962	to allow for extremely high load situations, but want to free resources
		1963	under normal circumstances (1000 threads can easily consume 30MB of RAM).
		1964
		1965	The default is probably ok in most situations, especially if thread
		1966	creation is fast. If thread creation is very slow on your system you might
		1967	want to use larger values.
		1968
		1969	=item IO::AIO::idle_timeout $seconds
		1970
		1971	Sets the minimum idle timeout (default 10) after which worker threads are
		1972	allowed to exit. SEe C<IO::AIO::max_idle>.
		1973
971	=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs	1974	=item IO::AIO::max_outstanding $maxreqs
		1975
		1976	Sets the maximum number of outstanding requests to C<$nreqs>. If
		1977	you do queue up more than this number of requests, the next call to
		1978	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		1979	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		1980	longer exceeded.
		1981
		1982	In other words, this setting does not enforce a queue limit, but can be
		1983	used to make poll functions block if the limit is exceeded.
972		1984
973	This is a very bad function to use in interactive programs because it	1985	This is a very bad function to use in interactive programs because it
974	blocks, and a bad way to reduce concurrency because it is inexact: Better	1986	blocks, and a bad way to reduce concurrency because it is inexact: Better
975	use an C<aio_group> together with a feed callback.	1987	use an C<aio_group> together with a feed callback.
976		1988
977	Sets the maximum number of outstanding requests to C<$nreqs>. If you	1989	Its main use is in scripts without an event loop - when you want to stat
978	to queue up more than this number of requests, the next call to the	1990	a lot of files, you can write somehting like this:
979	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
980	function will block until the limit is no longer exceeded.
981		1991
982	The default value is very large, so there is no practical limit on the	1992	IO::AIO::max_outstanding 32;
983	number of outstanding requests.
984		1993
985	You can still queue as many requests as you want. Therefore,	1994	for my $path (...) {
986	C<max_oustsanding> is mainly useful in simple scripts (with low values) or	1995	aio_stat $path , ...;
987	as a stop gap to shield against fatal memory overflow (with large values).	1996	IO::AIO::poll_cb;
		1997	}
		1998
		1999	IO::AIO::flush;
		2000
		2001	The call to C<poll_cb> inside the loop will normally return instantly, but
		2002	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2003	some requests have been handled. This keeps the loop from pushing a large
		2004	number of C<aio_stat> requests onto the queue.
		2005
		2006	The default value for C<max_outstanding> is very large, so there is no
		2007	practical limit on the number of outstanding requests.
988		2008
989	=back	2009	=back
990		2010
		2011	=head3 STATISTICAL INFORMATION
		2012
		2013	=over
		2014
		2015	=item IO::AIO::nreqs
		2016
		2017	Returns the number of requests currently in the ready, execute or pending
		2018	states (i.e. for which their callback has not been invoked yet).
		2019
		2020	Example: wait till there are no outstanding requests anymore:
		2021
		2022	IO::AIO::poll_wait, IO::AIO::poll_cb
		2023	while IO::AIO::nreqs;
		2024
		2025	=item IO::AIO::nready
		2026
		2027	Returns the number of requests currently in the ready state (not yet
		2028	executed).
		2029
		2030	=item IO::AIO::npending
		2031
		2032	Returns the number of requests currently in the pending state (executed,
		2033	but not yet processed by poll_cb).
		2034
		2035	=back
		2036
		2037	=head3 MISCELLANEOUS FUNCTIONS
		2038
		2039	IO::AIO implements some functions that are useful when you want to use
		2040	some "Advanced I/O" function not available to in Perl, without going the
		2041	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2042	counterpart.
		2043
		2044	=over 4
		2045
		2046	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2047
		2048	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2049	but is blocking (this makes most sense if you know the input data is
		2050	likely cached already and the output filehandle is set to non-blocking
		2051	operations).
		2052
		2053	Returns the number of bytes copied, or C<-1> on error.
		2054
		2055	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2056
		2057	Simply calls the C<posix_fadvise> function (see its
		2058	manpage for details). The following advice constants are
		2059	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2060	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2061	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2062
		2063	On systems that do not implement C<posix_fadvise>, this function returns
		2064	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2065
		2066	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2067
		2068	Simply calls the C<posix_madvise> function (see its
		2069	manpage for details). The following advice constants are
		2070	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2071	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>,
		2072	C<IO::AIO::MADV_FREE>.
		2073
		2074	On systems that do not implement C<posix_madvise>, this function returns
		2075	ENOSYS, otherwise the return value of C<posix_madvise>.
		2076
		2077	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2078
		2079	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2080	$scalar (see its manpage for details). The following protect
		2081	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2082	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2083
		2084	On systems that do not implement C<mprotect>, this function returns
		2085	ENOSYS, otherwise the return value of C<mprotect>.
		2086
		2087	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2088
		2089	Memory-maps a file (or anonymous memory range) and attaches it to the
		2090	given C<$scalar>, which will act like a string scalar. Returns true on
		2091	success, and false otherwise.
		2092
		2093	The scalar must exist, but its contents do not matter - this means you
		2094	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2095	the scalar first.
		2096
		2097	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2098	which don't change the string length, and most read-only operations such
		2099	as copying it or searching it with regexes and so on.
		2100
		2101	Anything else is unsafe and will, at best, result in memory leaks.
		2102
		2103	The memory map associated with the C<$scalar> is automatically removed
		2104	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2105	or C<IO::AIO::munmap> functions are called on it.
		2106
		2107	This calls the C<mmap>(2) function internally. See your system's manual
		2108	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2109
		2110	The C<$length> must be larger than zero and smaller than the actual
		2111	filesize.
		2112
		2113	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2114	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2115
		2116	C<$flags> can be a combination of
		2117	C<IO::AIO::MAP_SHARED> or
		2118	C<IO::AIO::MAP_PRIVATE>,
		2119	or a number of system-specific flags (when not available, the are C<0>):
		2120	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2121	C<IO::AIO::MAP_LOCKED>,
		2122	C<IO::AIO::MAP_NORESERVE>,
		2123	C<IO::AIO::MAP_POPULATE>,
		2124	C<IO::AIO::MAP_NONBLOCK>,
		2125	C<IO::AIO::MAP_FIXED>,
		2126	C<IO::AIO::MAP_GROWSDOWN>,
		2127	C<IO::AIO::MAP_32BIT>,
		2128	C<IO::AIO::MAP_HUGETLB> or
		2129	C<IO::AIO::MAP_STACK>.
		2130
		2131	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2132
		2133	C<$offset> is the offset from the start of the file - it generally must be
		2134	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2135
		2136	Example:
		2137
		2138	use Digest::MD5;
		2139	use IO::AIO;
		2140
		2141	open my $fh, "<verybigfile"
		2142	or die "$!";
		2143
		2144	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2145	or die "verybigfile: $!";
		2146
		2147	my $fast_md5 = md5 $data;
		2148
		2149	=item IO::AIO::munmap $scalar
		2150
		2151	Removes a previous mmap and undefines the C<$scalar>.
		2152
		2153	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2154
		2155	Calls the C<munlock> function, undoing the effects of a previous
		2156	C<aio_mlock> call (see its description for details).
		2157
		2158	=item IO::AIO::munlockall
		2159
		2160	Calls the C<munlockall> function.
		2161
		2162	On systems that do not implement C<munlockall>, this function returns
		2163	ENOSYS, otherwise the return value of C<munlockall>.
		2164
		2165	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2166
		2167	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2168	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2169	should be the file offset.
		2170
		2171	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2172	silently corrupt the data in this case.
		2173
		2174	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2175	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2176	C<IO::AIO::SPLICE_F_GIFT>.
		2177
		2178	See the C<splice(2)> manpage for details.
		2179
		2180	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2181
		2182	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2183	description for C<IO::AIO::splice> above for details.
		2184
		2185	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2186
		2187	Attempts to query or change the pipe buffer size. Obviously works only
		2188	on pipes, and currently works only on GNU/Linux systems, and fails with
		2189	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2190	size on other systems, drop me a note.
		2191
		2192	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2193
		2194	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2195	C<$flags> is missing or C<0>, then this should be the same as a call to
		2196	perl's built-in C<pipe> function and create a new pipe, and works on
		2197	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2198	(..., 4096, O_BINARY)>.
		2199
		2200	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2201	the given flags (Linux 2.6.27, glibc 2.9).
		2202
		2203	On success, the read and write file handles are returned.
		2204
		2205	On error, nothing will be returned. If the pipe2 syscall is missing and
		2206	C<$flags> is non-zero, fails with C<ENOSYS>.
		2207
		2208	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2209	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2210	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2211
		2212	=back
		2213
991	=cut	2214	=cut
992		2215
993	# support function to convert a fd into a perl filehandle
994	sub _fd2fh {
995	return undef if $_[0] < 0;
996
997	# try to generate nice filehandles
998	my $sym = "IO::AIO::fd#$_[0]";
999	local *$sym;
1000
1001	open *$sym, "+<&=$_[0]" # usually works under any unix
1002	or open *$sym, "<&=$_[0]" # cygwin needs this
1003	or open *$sym, ">&=$_[0]" # or this
1004	or return undef;
1005
1006	*$sym
1007	}
1008
1009	min_parallel 8;	2216	min_parallel 8;
1010		2217
1011	END {	2218	END { flush }
1012	min_parallel 1;
1013	flush;
1014	};
1015		2219
1016	1;	2220	1;
1017		2221
		2222	=head1 EVENT LOOP INTEGRATION
		2223
		2224	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2225	automatically into many event loops:
		2226
		2227	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2228	use AnyEvent::AIO;
		2229
		2230	You can also integrate IO::AIO manually into many event loops, here are
		2231	some examples of how to do this:
		2232
		2233	# EV integration
		2234	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2235
		2236	# Event integration
		2237	Event->io (fd => IO::AIO::poll_fileno,
		2238	poll => 'r',
		2239	cb => \&IO::AIO::poll_cb);
		2240
		2241	# Glib/Gtk2 integration
		2242	add_watch Glib::IO IO::AIO::poll_fileno,
		2243	in => sub { IO::AIO::poll_cb; 1 };
		2244
		2245	# Tk integration
		2246	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2247	readable => \&IO::AIO::poll_cb);
		2248
		2249	# Danga::Socket integration
		2250	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2251	\&IO::AIO::poll_cb);
		2252
1018	=head2 FORK BEHAVIOUR	2253	=head2 FORK BEHAVIOUR
1019		2254
1020	This module should do "the right thing" when the process using it forks:	2255	Usage of pthreads in a program changes the semantics of fork
		2256	considerably. Specifically, only async-safe functions can be called after
		2257	fork. Perl doesn't know about this, so in general, you cannot call fork
		2258	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2259	pthreads, so this applies, but many other extensions and (for inexplicable
		2260	reasons) perl itself often is linked against pthreads, so this limitation
		2261	applies to quite a lot of perls.
1021		2262
1022	Before the fork, IO::AIO enters a quiescent state where no requests	2263	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1023	can be added in other threads and no results will be processed. After	2264	only works in the process that loaded it. Forking is fully supported, but
1024	the fork the parent simply leaves the quiescent state and continues	2265	using IO::AIO in the child is not.
1025	request/result processing, while the child frees the request/result queue
1026	(so that the requests started before the fork will only be handled in the
1027	parent). Threads will be started on demand until the limit set in the
1028	parent process has been reached again.
1029		2266
1030	In short: the parent will, after a short pause, continue as if fork had	2267	You might get around by not I<using> IO::AIO before (or after)
1031	not been called, while the child will act as if IO::AIO has not been used	2268	forking. You could also try to call the L<IO::AIO::reinit> function in the
1032	yet.	2269	child:
		2270
		2271	=over 4
		2272
		2273	=item IO::AIO::reinit
		2274
		2275	Abandons all current requests and I/O threads and simply reinitialises all
		2276	data structures. This is not an operation supported by any standards, but
		2277	happens to work on GNU/Linux and some newer BSD systems.
		2278
		2279	The only reasonable use for this function is to call it after forking, if
		2280	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2281	the process will result in undefined behaviour. Calling it at any time
		2282	will also result in any undefined (by POSIX) behaviour.
		2283
		2284	=back
1033		2285
1034	=head2 MEMORY USAGE	2286	=head2 MEMORY USAGE
1035		2287
1036	Per-request usage:	2288	Per-request usage:
1037		2289
…		…
1039	bytes of memory. In addition, stat requests need a stat buffer (possibly	2291	bytes of memory. In addition, stat requests need a stat buffer (possibly
1040	a few hundred bytes), readdir requires a result buffer and so on. Perl	2292	a few hundred bytes), readdir requires a result buffer and so on. Perl
1041	scalars and other data passed into aio requests will also be locked and	2293	scalars and other data passed into aio requests will also be locked and
1042	will consume memory till the request has entered the done state.	2294	will consume memory till the request has entered the done state.
1043		2295
1044	This is now awfully much, so queuing lots of requests is not usually a	2296	This is not awfully much, so queuing lots of requests is not usually a
1045	problem.	2297	problem.
1046		2298
1047	Per-thread usage:	2299	Per-thread usage:
1048		2300
1049	In the execution phase, some aio requests require more memory for	2301	In the execution phase, some aio requests require more memory for
…		…
1054		2306
1055	Known bugs will be fixed in the next release.	2307	Known bugs will be fixed in the next release.
1056		2308
1057	=head1 SEE ALSO	2309	=head1 SEE ALSO
1058		2310
1059	L<Coro::AIO>.	2311	L<AnyEvent::AIO> for easy integration into event loops, L<Coro::AIO> for a
		2312	more natural syntax.
1060		2313
1061	=head1 AUTHOR	2314	=head1 AUTHOR
1062		2315
1063	Marc Lehmann <schmorp@schmorp.de>	2316	Marc Lehmann <schmorp@schmorp.de>
1064	http://home.schmorp.de/	2317	http://home.schmorp.de/

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